The most common form of vitamin B12 is called cyanocobalamin. However, over the last ten years, a number of central and peripheral neurological diseases have been linked to a deficiency of a very specific cobalamin, the methylcobalamin form, that is required to protect against neurological diseases and aging. The liver converts a small amount of cyanocobalamin into methylcobalamin within the body, but larger amounts of methylcobalamin are necessary to correct neurological defects and protect against aging.